Barcode reader is widely used in the industry for reading a message on a barcode adhered on an object. However, in operation, errors are frequently found, especially when the barcode reader is not closed enough to the barcode for detection. Moreover, it is required to project light on the barcode for the barcode reader to read.
Recently, it is found that radio frequency identification (RFID) techniques have been applied to many applications for easily obtaining messages on an object. The message is stored in a RFID tag and a signal is transmitted wirelessly from the RFID tag to a RFID reader within an effective transmission distance. A large amount of messages can be transmitted by radio frequency identification. It is very simple and convenient to read a message by RFID.
Passive RFID transponders or tags, instead of the conventional barcode tags, are used to communicate messages for product tracking. The use of passive RFID tags includes the mounting of the RFID tags in the packaging of wine bottles and corks in which the RFID tags carry anti-counterfeit and product-tracking information. Once the cork of a wine bottle is removed, the RFID tag mounted thereof is destroyed simultaneously; hence a RFID reader receives no signals from the destroyed RFID tag. It is also easy for the RFID reader to identify a counterfeit wine that would not send messages to the RFID reader. Hence, any opened wine or counterfeit wine is recognized and prevented. However, it is noted that once the RFID tag is destroyed, whether it is destroyed intentionally by the consumer or unintentionally by the manufacturing machine or workers, the RFID reader is not able to read any information from the RFID tag, and hence not able to track the product.
U.S. Pat. No. 6,486,780 discloses applications for radio frequency identification systems. RFID devices, including handheld RFID devices, and applications may be used in connections with items that are associated with an RFID tag, and optionally a magnetic security element. The devices and applications can be applied for management of books and materials in a library.
A multi-directional RFID antenna is disclosed in U.S. Pat. No. 6,069,564. The antenna provides multi-directional RF communication to a source, such as a RF tag, which comprises a plurality of coils for transmission of RF signals and a switch for selecting at least one of the RF antenna coils for transmission of the RF signal and receipt of the RF response signals whereby the RF signals can be directed toward and received from a plurality of different directions from a fixed position.
In WO 2006/049374A1, a RFID sensor is disclosed. The RFID sensor comprises a plurality of RFID chips for monitoring different objects e.g. gas valve, door, window and so on. The RFID reader transmits a radio frequency signal to the RFID sensor at a predetermined period, and receives a frequency signal having the unique number of the chosen RFID chip from the RFID sensor. Then the RFID reader transmits the signal to the controller to recognize the used state of the monitored object. The controller can provide the information, e.g. “the gas valve is open”, to the user through a Personal Digital Assistance. The system also comprises a selection unit for choosing the chip by a physical or an electrical operation and connecting the chosen chip to the RFID antenna. Therefore, the accessing of information from the chips is controlled to assure safety. The system requires a plurality of RFID tags that increase the manufacture cost. Moreover, the system is unable to realize whether the RFID tags that are connected to the antenna work normally or not.
Taiwan Patent No. 494245 discloses a radio frequency identification tag device having a sensor input adapted to receive variable signals from a sensor which may be a switch, a transistor, a hall effect device, a photo-transistor and the like. The difference between the two data word bit streams represent the change in the sensor (open or closed) which represents whatever the sensor represents, i.e., open or closed valve, circuit breaker on or tripped, and the like. The sensor input modifies the tag data word bit stream. In the patent, a register is arranged in the logic circuit for reading and/or writing information.
The conventional security systems for detecting the ON/OFF status of a switch mainly adopt wired configuration. It is desired to provide a detection device that is able to detect the status of a switch, control or monitor the ON/OFF of a switch wirelessly that is simple for installation and is cheap in manufacturing cost.